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Caliber logo
Caliber Library.jpg
Caliber interface under Windows 7
Basic data

developer Kovid Goyal
Publishing year October 31, 2006
Current  version 4.22.0
( July 31, 2020 )
operating system Linux , macOS , Windows
programming language Python , C.
category E-book management
License GNU GPLv3

Caliber is a free program package for processing, converting and managing e-books for Linux , macOS and Windows . In many Linux distributions , the software can be installed directly from the standard package sources .


The Indians Kovid Goyal began development on 31 October 2006, during the US - launch of the e-book reader PRS-500 from Sony, initially without graphical user interface and under the name "libprs500". In order to make this reader usable under Linux, Goyal reconstructed the communication protocol for accessing the device via USB with support from the MobileRead community and wrote a converter for the proprietary file format LRF used .

In mid-2008 the name was changed to today's "caliber".

Caliber viewer


The large number of (mostly also in writing) supported file formats contains most of the currently relevant formats, which can be displayed , printed out and converted to a very large extent in a configurable manner . The contents can also be edited, for example by changing the font to be used or inserting an automatically created table of contents.

Caliber offers a variety of features for cataloging and managing collections of electronic books. They can be provided with various properties and metadata . The latter can also be filled in automatically from various sources ( ISBNdb .com, Google Books , Amazon , LibraryThing ).

The books can be imported into Caliber and exported to various mobile devices . It is possible to synchronize books and metadata, whereby they are automatically converted into appropriate data formats.

Messages from news websites ( web feeds ) can be automatically obtained from the Internet , packed into an e-book file and transmitted to a mobile device. Wikipedia articles can also be saved as EPUB documents with the help of a wiki reader.

The support of file formats, mobile devices, news and metadata sources is modularly expandable.

The content of the managed collection is also available remotely via the Internet, web browser , mobile device, etc. or can (for example, subscribed content) be automatically delivered (“push”).

  • From version 0.9.34 onwards, texts in docx format can be converted to EPUB using Caliber .
  • From version 1.15 onwards, electronic books in the formats EPUB and AZW3 ( Kindle ) can be edited using Caliber .
  • From version 1.22 on it is possible to compare the content of e-book files.
  • From version 2.0 on, e-book files can be created in EPUB and AZW3 formats and existing electronic books can be edited.
  • With version 3.0 from June 2017, a completely new "content server" was created that allows books to be read in the browser of a smartphone or tablet in offline mode.
  • With version 4.0 from October 2019, Qt WebKit was migrated to Qt WebEngine because Qt WebKit is no longer serviced. As a result of this change, some parts of Caliber had to be rewritten.
  • With version 4.9.1 from January 2020 the search functionality has been improved so that regular expressions are now supported.
  • With version 4.14 from April 2020, the search functionality has been further improved so that fuzzy searches are now supported.


The application is written in the programming languages Python and C and is published under the conditions of version 3 of the GNU General Public License (GPL) as free software, including the source code .

For message retrieval is Caliber operated as RSS - Feed Reader ; for remote access it contains e-mail and web servers ( HTTP ).

The software is also available as a portable version. From version 0.9.9 on there is also a 64-bit version for Windows.

The functionality can be expanded with various plug-ins (e.g. DeDRM or EpubMerge).

Web links

Commons : Caliber  - collection of images, videos and audio files

Individual evidence

  1. .
  2. Release 4.22.0 . July 31, 2020 (accessed August 1, 2020).
  7. caliber - What's new. Retrieved November 30, 2017 .
  9. caliber - New in caliber 3.0. Retrieved November 30, 2017 .
  10. caliber - New in caliber 4.0. Retrieved February 25, 2020 .
  11. caliber - What's new - Major new features. Retrieved February 25, 2020 .
  12. caliber - What's new - Changelog. Retrieved April 29, 2020 .
  14. see